Quantitative chemical study of root canal preparations with calcium hydroxide

Abstract Chemical tests were carried out in order to determine the rate of carbonatation of different samples of calcium hydroxide used in intracanal therapeutics. The methods were based either on direct measurement of the kinetics of CO₂ fixation by dry powder or on analytical titration of the carbonate content of fresh and aged samples. Dry powder preserved in closed flasks and paste preparations packed in screw syringes were free from carbonate even after several years. When samples were exposed to open air the rate of carbonatation was extremely slow. The carbonate formation in normal clinical conditions of calcium hydroxide utilization seemed not to be responsible for the variability sometimes observed in clinical results.     

氢氧化钙在根管消毒中的作用机制

氢氧化钙因其特有的理化特性在临床根管消毒中得到越来越广泛的应用。许多研究表明,氢氧化钙具有良好的扩散性,并可以通过破坏细菌菌体、降解细菌脂多糖等途径发挥消毒作用。本文将对氢氧化钙在根管消毒中的主要作用机制做一综述。     

Alveolar mucosa necrosis induced by utilisation of calcium hydroxide as root canal dressing

This case demonstrates the ability of calcium hydroxide to cause connective tissue necrosis. A patient with a history of trauma exhibited a large area of external inflammatory root resorption affecting the cervical and middle thirds of tooth 12. After root canal cleaning, a calcium hydroxide root canal dressing was applied to control the resorption process. After three days when the patient attended for replacement of the dressing an irregular zone of necrosis was observed on the buccal aspect of the alveolar mucosa. Careful curettage and irrigation was then performed to remove the extruded calcium hydroxide and necrotic tissue. After curettage, the root canal was accessed and irrigated with saline solution for removal of remnants of the dressing. The dressing was than replaced taking care to avoid contact with soft tissue, which might induce further damage, minimising the overflow of material. Improvement in healing was observed at 15-day follow-up, with complete closure of the lesion by soft tissue. At the 120-day follow-up, no scar was detected. At 180-day follow-up, the root canal was filled only with mineral trioxide aggregate (MTA) with aid of K files #20 and #50. At two-year follow-up, there were no symptoms and the resorption process seemed to have ceased. It is important to emphasise the damage that may occur when calcium hydroxide is in close and extended contact with the soft tissues, which could happen when dressing material is extruded through a root resorption.     

氢氧化钙用于根管封药的动物实验研究

目的：比较氢氧化钙和甲醛甲酚（FC）对去髓术和根管治疗术的封药效果。方法：将Wistar大鼠的下颌第一磨牙作实验牙，制备根尖周病动物模型。用氢氧化钙糊剂和FC分别封人实验牙近中根管进行去髓术和根管治疗术，术后分别观察1、2、3、6和10周。结果：去髓术组中，FC组早期有炎症反应，氢氧化钙组炎症反应较轻；10周时氢氧化钙组出现根尖周骨质新生。根管治疗术组中，以FC组的尖周炎症消退最快，氢氧化钙组次之，3周时两组的炎症均消失，10周时氢氧化钙组出现根尖骨质新生。结论：氢氧化钙作为去髓术和根管治疗术中的根管封药具有较理想的药理作用。     

���������������΢��©Ӱ�����ص��о���״

提要：根管治疗术后根尖发生微渗漏是导致根管治疗失败常见的原因之一。根管治疗术后根尖微渗漏的影响因素有很多, 包括根管预备及充填方法、玷污层的处理、根充材料等。本文对此做一综述。     

Long-term calcium hydroxide as a root canal dressing may increase risk of root fracture

Abstract – It has been proposed (Cvek 1992) that immature teeth are weakened by filling of the root canals with calcium hydroxide dressing and gutta-percha. The aim of the present study was to test the hypothesis that dentin in contact with calcium hydroxide would show a reduction in fracture strength after a certain period of time. Immature mandibular incisors from sheep were extracted and divided into two experimental groups. Group 1: the pulps were extirpated via the apical foramen. The root canals were then filled with calcium hydroxide (Calasept^®) and sealed with IRM^® cement, and the teeth were then stored in saline at room temperature for 0.5, 1, 2, 3, 6, 9, or 12 months. Group 2: the pulps were extirpated and the root canals were filled with saline and sealed with IRM^® cement. The teeth were then stored in saline for 2 months. Intact teeth served as controls and were tested immediately after extraction. All teeth were tested for fracture strength in an Instron testing machine at the indicated observation periods. The results showed a markedly decrease in fracture strength with increasing storage time for group 1 (calcium hydroxide dressing). The results indicate that the fracture strength of calcium hydroxide-filled immature teeth will be halved in about a year due to the root filling. The finding may explain the frequent reported fractures of immature teeth filled with calcium hydroxide for extended periods.     

A clinical evaluation of one and two-appointment root canal therapy using calcium hydroxide

A clinical study using vital maxillary central incisors was performed to evaluate the incidence of postoperative pain after root canal treatment in one- or two-appointments using a calcium hydroxide-containing root canal sealer. No differences were observed between the two groups.     

In vivo sealing ability of calcium hydroxide-containing root canal sealers

Abstract It was the purpose of this study to determine the sealing ability of 2 commercially available calcium hydroxide-containing root canal sealers, CRCS and Sealapex. One hundred sixty single-rooted human teeth were used. The clinical crowns were removed and the roots were cleaned mechanically and by immersion for 24 h in 5% sodium hypochlorite. The root canals were then instrumented to size 80 at the apical foramen and the roots were sterilized by γ-radiation. Under aseptic conditions the root canals were filled with a gutta-percha master cone size 70 and Sealapex (48 roots), CRCS (48 roots), and a zinc oxide-eugenol type sealer, Roth 801 (50 roots). The coronal aspects of the root canals were then sealed with zinc oxide-eugenol cement. In order to bring the roots and root filling materials in contact with tissue and tissue fluids, the roots were implanted subcutaneously in rabbits for 90 days and 1 year. Leakage as demonstrated by penetration of India ink was evaluated using a stereomicroscope. The best results were obtained with CRCS. Significantly less leakage occurred with both calcium hydroxide-containing sealers than with the traditional zinc oxide-eugenol sealer.     

氢氧化钙糊剂清洁根管壁的扫描电镜研究

目的 :观察氢氧化钙糊剂对根管壁的清洁作用。方法 :取离体人牙的根 1/ 3,劈开后分别浸入 5 2 .5g/L次氯酸钠液中 5、15s和氢氧化钙水糊剂中 1、3、7d ,超声清洗后扫描电镜观察。结果 :次氯酸钠 5s和氢氧化钙 1d组牙髓未完全溶解 ,氢氧化钙 3d时尚有少量牙髓组织、前期牙本质未溶解。氢氧化钙 7d和次氯酸钠处理 15s时 ,牙髓彻底溶解 ,根管壁平整 ,牙本质小管口完全暴露。结论 :氢氧化钙具有较好的根管壁清洁作用     

Monoinfection of root canal with Pseudomonas aeruginosa

Abstract A successful treatment of a persisting endodontic infection with Pseudomonas aeruginosa is described together with a review of its presence in saliva and root canal infections. The treatment included ethanol irrigation and prolonged calcium hydroxide therapy in addition to thorough mechanical preparation. The minimum pH value of calcium hydroxide for in vitro killing of the isolated strain was found to be above 10.     

Effect of root canal filling materials containing calcium hydroxide on the alkalinity of root dentin

Abstract The effect of root canal filling pastes containing calcium oxide resp. calcium hydroxide on the alkalinity of extracted human teeth was investigated using a colour indicator (cresol red). An aqueous suspension of calcium hydroxide (Pulpdent), which is normally used for temporary root canal filling, most consistently produced alkalinity. Removal of the smear layer following instrumentation of the root canal led to increased proportion of alkaline-positive spots in dentinal locations distant from the canal. A clearly smaller effect was found with a calcium salicylate cement (Sealapex) and an oil-paste (Gangraena Merz), both of which are available for definite root canal fillings. Following removal of the smear layer, these hard-setting preparations caused moderate alkalinity in dentin adjacent to the canal but no effect was observed in locations more distant from the canal. Neither at locations adjacent to nor distant from the root canal was alkalinity found when another calcium salicylate cement (Apexit) was used. Apparently the release of hydroxyl ions into root dentin from calcium hydroxide containing root canal filling materials is not solely influenced by the absolute amount of calcium hydroxide, but also depends on other ingredients which variably inhibit the release of these ions.     

Effect of calcium hydroxide dressing on seal of permanent root filling

Abstract Low apical leakage along root fillings following an application of calcium hydroxide was reported in a few methylene blue dye penetration studies. It has been found recently that methylene blue is decolored by calcium hydroxide, indicating that the short penetration of methylene blue may not be due to a tight seal only. Of the 80 roots of human maxillary central incisors used in this study, 40 roots (group 1) received calcium hydroxide root canal dressing whereas another 40 roots (group 2) did not. All the roots were then obturated with gutta-percha and Tubli-Seal sealer. Leakage along 20 filled roots in each group was measured using a modified fluid transport model at 48 h, 2, 4, 8 and 16 weeks after obturation; whereas leakage of another 20 filled roots in each group was measured using dye penetration with 1% methylene blue. Using the fluid transport model, no significant difference was found between the two groups at any time interval (P=0.4847, 0.3875, 0.9490, 0.4786, 0.9148 respectively after 48 h, 2, 4, 8 and 16 weeks); using the methylene blue penetration method, leakage in group 1 (with root canal dressing) was significantly less than that in group 2 (without root canal dressing) P=0.0374). The contradiction in results from the different models indicated that problems existed with the models.     

Clinical investigation of the effect of calcium hydroxide intracanal dressing on bacterial lipopolysaccharide reduction from infected root canals

The purpose of this clinical study was to determine the effect of 7 day intracanal dressing with calcium hydroxide on the amount of bacterial lipopolysaccharide (LPS; endotoxin) in human teeth with necrotic and infected pulp and apical periodontitis. Twenty‐five single‐rooted teeth with necrotic pulps and apical periodontitis were selected. Samples were collected before (S1), after root canal preparation (S2) and after 7 day intracanal dressing with calcium hydroxide (S3). The limulus amoebocyte lysate assay was used to quantify LPS. LPS was present in 100% of the root canals before (S1), after preparation (S2) and after 7 day intracanal dressing (S3). A significant reduction, equal to 29.54%, was found after root canal preparation (P < 0.05). A significant difference (equal to 25.26% reduction) was also detected between S2 and S3 (P < 0.05). Total endotoxin reduction (S3 compared with S1) was found to be 47.34%. Endotoxin concentration of the infected root canals was reduced after root canal preparation and also after 7 days of dressing of canals with calcium hydroxide; however, relatively high values of endotoxin remained in the root canals.     

An in vitro comparison of pH changes in root dentine following canal dressing with calcium hydroxide points and a conventional calcium hydroxide paste

AIM: This study aimed to measure and compare pH changes at apical and cervical sites on the external root surface of extracted teeth dressed with calcium hydroxide in two different formulations. METHODOLOGY: Root canals of 45 single-rooted extracted human teeth were accessed and shaped using a step-down technique with rotary instrumentation. Standard cavities were prepared on the external root surface at specific apical and cervical sites. The teeth were randomly allocated to three groups. Teeth in group A were dressed with calcium hydroxide points, those in group B were dressed with an aqueous calcium hydroxide paste and teeth in group C were left unfilled. Following storage in humid conditions, the pH of the dentine at apical and cervical sites was measured at baseline and then at 24 h, 72 h, 1 week, 10 days, 2 weeks and 3 weeks. RESULTS: The pH of the root dentine at both apical and cervical sites was significantly greater (P < 0.001) in teeth dressed with aqueous calcium hydroxide paste compared with those dressed with calcium hydroxide points, when averaged out across all time periods. For all groups, there was a significant difference between the mean apical and cervical pH values for each tooth with lower values for the apical sites (P < 0.001). CONCLUSION: The results of this study indicate that an aqueous calcium hydroxide paste was more effective than calcium hydroxide points at raising the pH on the external root surface of extracted teeth.     

改良氢氧化钙糊剂与甲醛甲酚在根管消毒中的抗菌效果比较

目的：进一步探讨氢氧化钙对感染根管消毒的抗菌效果。方法：实验组８０牙乃入良氢氧化钙糊剂封入根管的消毒;对照组８０牙封入甲醛甲酚。观察其临床疗效与细菌学变化。结果：１月后实验组根管消毒作用明显优于对照组。１周后抗菌作用实验组与对照组杀菌力相当。结论：氢氧化钙对感染根管消毒具有良好的抗菌效果。     

Solubility and biocompatibility of calcium hydroxide-containing root canal sealers

Abstract The solubility and biocompatibility of 2 commercially available calcium hydroxide-containing root canal sealers, CRGS and Sealapex, were studied. Four dogs were anesthetized and a sulcular incision was made to expose the vestibular surface of the mandble. Two rows of holes, 2 mm deep, 2 mm wide and 10 mm apart, were drilled into the mandible. Teflon cups with the same dimensions as the holes were filled with the experimental materials and placed in the cavities. For the purpose of comparison, Teflon cups filled with a traditional zinc oxide-eugenol sealer and a paste of calcium hydroxide and saline were implanted as well. After 90 days the animals were killed. The mandibles were dissected free, fixed in formalin and demineralized. Bone specimens containing 1 Teflon cup were then embedded in paraffin, sectioned longitudinally, and the sections were stained with hematoxylin and eosin and examined in the light microscope. The cups which originally contained the paste of calcium hydroxide and saline were completely filled with bone. Sealapex was partly missing from the cups and was generally replaced by ingrowth of connective tissue. Large amounts of the material were seen in macrophages and tissue outside the cups. CRCS and the traditional zinc oxide-eugenol sealer generally filled the cups well after 3 months. Tissue fluids were seen in the superficial layers of these materials, but ingrowth of tissue had not occurred. No macrophage reaction was seen with either of these materials, but a stronger inflammatory reaction was caused by CRCS than by the traditional zinc oxide-eugenol cement. CRCS appeared to be the most stable of the calcium hydroxide-containing sealers tested.     

A laboratory study evaluating the release of hydroxyl ions from various calcium hydroxide products in narrow root canal-like tubes

AIM: The aim of the present study was to describe pH changes in a variety of buffering solutions within a narrow test tube containing either a gutta-percha point with incorporate calcium hydroxide, a commercial calcium hydroxide paste (Calcicur) or a freshly mixed paste of calcium hydroxide in distilled water. METHODOLOGY: The test material was placed centrally in a test tube of 2 mm inner diameter. Saline (1%) was placed at one end, whilst the buffering solutions were introduced at the other. The pH of the buffering solutions was monitored using electrodes placed at each end of the test tube. RESULTS: It was found that the pH 4.01 buffer strongly resisted pH changes at levels below 6.0, whilst saliva and bovine serum was buffered less and more evenly in the whole range up to pH 11.5. The calcium hydroxide containing gutta-percha points caused the pH to increase quickly in the sodium chloride solution to levels above 11.5. However, in bovine serum, in saliva and in the pH 4.01 buffer the pH remained below 8.5, 8.0 and 6.0, respectively, 1 mm from the point. In contrast, the release of hydroxyl ions from the two calcium hydroxide pastes brought pH above pH 11.5 irrespective of the buffering of the solutions 5 mm from the paste. CONCLUSION: It is concluded that Calcicur and the calcium hydroxide-water mixture contained substantially more available calcium hydroxide than did the calcium hydroxide containing gutta-percha points, with the result that the release of hydroxyl ions from the points was limited in comparison to that from the pastes.     

Effects of instrumentation, irrigation and dressing with calcium hydroxide on infection in pulpless teeth with periapical bone lesions

AIM: The aim of this study was to evaluate the fate of microorganisms in root canals of teeth with infected pulps and periapical bone lesions with and without the use of calcium hydroxide medication. METHODOLOGY: Endodontic samples were cultured and microorganisms were counted and identified in 43 teeth before (sample 1) and after (sample 2) treatment during the first visit and before (sample 3) and after (sample 4) treatment during the second visit. In the first visit teeth were instrumented and half of the teeth were filled with a thick slurry of calcium hydroxide in sterile saline. The other teeth were obturated with gutta-percha and AH-2 6 sealer. After 4 weeks the teeth with calcium-hydroxide were accessed again and after microbiological sampling they were obturated with gutta-percha and AH-26 sealer. RESULTS: The mean total colony forming unit (CFU) counts of positive samples dropped significantly as a result of canal preparation during the first visit from 1.0 x 10(6) to 1.8 x 10(3) (between samples 1 and 2) but increased to 9.3 x 10(3) in the period between the two visits (sample 2 and 3). There was no difference in mean total CFU counts of positive samples between the end of the first (sample 2) and the end of the second visit (sample 4). The most frequently isolated species were Prevotella intermedia, Capnocytophaga spp.. Actinomyces odontolyticus. Propionibacterium acnes and Peptostreptococcus micros. CONCLUSIONS: Although a calcium hydroxide paste was placed in the prepared canals, the number of positive canals had increased in the period between visits. However, the number of microorganisms had only increased to 0.93% of the original number of CFU (sample 1). It is concluded that a calcium hydroxide and sterile saline slurry limits but does not totally prevent regrowth of endodontic bacteria.     

Calcium hydroxide root canal sealers: evaluation of pH, calcium ion concentration and conductivity

The calcium hydroxide ionization of four root canal sealers (Sealapex, CRCS, Sealer 26, and Apexit) was studied by measuring conductivity and pH and by conducting atomic absorption spectrophotometry. Samples 6 mm in diameter and 15 mm long were prepared from these sealers. After setting and 48 h storage in a desiccator, five samples of each material were placed in 50 mL distilled water and analysed after 0,1,2,4, 6 and 24 h and 5, 15 and 30 days. The results showed that Sealapex was the root canal sealer showing the highest pH, ionic calcium and total calcium values ( P <0.05) throughout the experimental period, followed by CRCS, Apexit and Sealer 26.     

Bacterial leakage in obturated root canals following the use of different intracanal medicaments

Abstract – The aim of this study was to examine whether intracanal medication prior to root canal obturation has an inhibitory effect on corono-apical penetration of bacteria. 93 single rooted teeth were instrumented and sterilized with ethylene oxide. They were assigned to three control groups and four test groups with n =20 each. For one week, they were dressed with different medicaments: The first group with a 5% chlorhexidine gel, the second with Ledermix, the third with a fresh mix of calcium hydroxide and water and the fourth without any medication. After obturation (lateral condensation, AH26) the roots were fixed between a top and a bottom chamber. The top chamber contained 3 mL trypticase soy broth with 10⁸ Staphylococcus epidermidis CFU's/mL, whereas the bottom chamber contained sterile trypticase soy broth. For one year, the mounts were incubated at 37°C. They were checked on a regular basis for turbidity in their bottom chambers indicating bacterial growth. None of the test samples leaked for three months. After one year, the calcium hydroxide group had only 6 leaking samples whereas the chlorhexidine group had 14, the Ledermix group 15, and the unmedicated group had 13 leaking samples. It may be concluded that under the conditions of this study, calcium hydroxide was the medicament of choice to avoid bacterial penetration of the root canal. Ledermix did not perform better than no pre-medication. Chlorhexidine was superior to Ledermix in the second third of the observation period.